The present invention relates to an optical transmitter-receiver module and an electronic device for use in a single-core bidirectional optical transmitter-receiver system capable of performing transmission and reception with a single-core optical fiber. The present invention relates, in particular, to a digital communication system, which is able to perform high-speed transmission, such as IEEE1394 (Institute of Electrical and Electronic Engineers 1394) and USB (Universal Serial Bus) 2.0.
Conventionally, as a first optical transmitter-receiver module, there is a one as described in Japanese Patent Laid-Open Publication No. 2001-116961. In this optical transmitter-receiver module, full-duplex communications are achieved by reducing electric crosstalk by employing a shield plate while reducing optical crosstalk by employing a light-tight partition plate that abuts against the end surface of the optical fiber so as to separate the light-emitting device and the light-receiving device from each other.
FIG. 35A and FIG. 36A are plan views of a partition plate 1019, while FIG. 35B and FIG. 36B are side views showing the positional relationship of the partition plate 1019 with respect to an optical plug 1030. With regard to this first optical transmitter-receiver module, FIGS. 35A and 35B shows a state in which the optical plug 1030 provided internally with a single-core optical fiber 1032 is partway inserted in an optical transmitter-receiver module (overall view is not shown) and starts coming in contact with the partition plate 1019. FIGS. 36A and 36B show a state in which the optical plug 1030 is completely inserted in the optical transmitter-receiver module and fully put in contact with the partition plate 1019.
FIG. 37A shows a side view of an essential part of an optical cable, which has the plug 1030 and constitutes an optical transmitter-receiver system with the aforementioned optical transmitter-receiver module, while FIG. 37B shows a rear view of the optical cable that has the optical plug 1030. As shown in FIGS. 37A and 37B, the optical plug 1030 (including the optical fiber) is provided at each end portion (only one end portion is shown) of the optical cable, and a front end of the optical plug 1030, which includes a tip of the optical fiber, has an inclined surface 1030a inclined forward in the lengthwise direction of the optical fiber (i.e., toward the other optical transmitter-receiver module side not shown). Moreover, the optical plug 1030 is provided with a anti-rotation key 1031 extended in the horizontal direction, and the optical transmitter-receiver module is internally provided with a keyway (not shown) that cooperates with the key 1031, for preventing possible changes in the optical input and characteristics in accordance with the rotation of the optical plug 1030.
Moreover, as a second conventional optical transmitter-receiver module, there is a one as described in Japanese Patent Laid-Open Publication No. 2001-147349. As shown in FIG. 38, this second optical transmitter-receiver module employs a partition plate 1111 similar to that of the aforementioned first conventional optical transmitter-receiver module that has an optical system employing a Foucault prism 1104. According to this, in the second optical transmitter-receiver module, the end surface of the optical fiber 1102 of the optical plug 1101 abuts against the partition plate 1111, and a light-emitting element 1103 and a light-receiving element 1105 are molded or encapsulated with a molding resin 1106. Lens portions 1106a and 1106b are integrally formed in the plastic molding stage of the molding resin.
In the aforementioned first conventional optical transmitter-receiver module, the optical plug 1030 has the anti-rotation key 1031. Therefore, the optical plug 1030 cannot be inserted into the optical transmitter-receiver module unless the key 1031 is aligned with the keyway of the optical transmitter-receiver module when fitting the optical plug 1030, and this disadvantageously causes inconvenience to the user. However, if the anti-rotation key 1031 of the optical plug 1030 is removed to improve the convenience at the time of insertion of the optical plug, then the optical plug 1030 becomes rotatable. Therefore, if the optical plug 1030 rotates with an optical fiber end surface 1030a being in contact with the partition plate 1019, then there occurs a problem that the inclined end surface 1030a of the optical fiber and/or the partition plate 1019 is damaged.
Moreover, the second conventional optical transmitter-receiver module, which employs the Foucault prism optical system having the partition plate 1111 similar to that of the first conventional optical transmitter-receiver module, has the structure in which the partition plate 1111 abuts against the end surface of the optical fiber 1102. Therefore, similarly to the first conventional optical transmitter-receiver module, there occurs a problem that the end surface of the optical fiber 1102 and/or the partition plate 1111 is damaged. Furthermore, the light-emitting element 1103 and the light-receiving element 1105 are mounted on an identical substrate 1109 in this second optical transmitter-receiver module, but the optical positions of the light-emitting element 1103 and the light-receiving element 1105 are not optimized with regard to the optical system that has the partition plate 1111.
Accordingly, an object of this invention is to provide an optical transmitter-receiver module and an electronic device using the same, which module is able to perform high-quality optical transmission by full-duplex communication scheme by using a light-tight partition plate and able to prevent the optical fiber end surface and the partition plate from being damaged even if the inserted optical plug is rotated in the module.
In order to accomplish the above object, the present invention provides an optical transmitter-receiver module having a light-emitting element for emitting transmission signal light and a light-receiving element for receiving reception signal light, said module being able to perform both transmission of the transmission signal light and reception of the reception signal light by means of a single-core optical fiber, said module comprising:
a jack section for detachably holding an optical plug provided at an end portion of the optical fiber;
a light emitting/receiving unit having the light-emitting element and light-receiving element positioned and fixed in place and molded in one piece; and
a light-tight partition plate unit for separating an optical path of the transmission signal light and an optical path of the reception signal light from each other, said light-tight partition plate being arranged so as to be held between the jack section and the light emitting/receiving unit,
the light-tight partition plate unit having spring means for urging this unit toward the optical fiber.
According to the optical transmitter-receiver module of the above construction, by arranging the light-tight partition plate unit for separation between the optical path of the transmission signal light and the optical path of the reception signal light so that the plate is held between the jack section and the light emitting/receiving unit, the coupling of the transmission signal light directly with the light-receiving element is restrained, so that high-quality optical transmission by the full-duplex communication method is achieved. Further, because the partition plate unit is always urged toward the optical fiber by the spring means, the positional relation between the end surface of the optical plug and the partition plate unit is kept constant. Therefore, high-quality optical transmission by the full-duplex communication scheme can be performed, and the optical fiber end surface and the partition plate are prevented from being damaged even if the inserted optical plug is rotated in the module.
In one embodiment, the partition plate unit has a partition plate for separating an optical path of the transmission signal light and an optical path of the reception signal light from each other, a resin-molded piece having an engagement surface with which an end surface of the optical plug comes in contact when inserted in the jack section, and the spring means urging the engagement surface of the resin-molded piece toward the optical plug. Also, the module further comprises a retaining portion for retaining the partition plate unit movably in a direction of optical axis of the optical fiber.
In this embodiment, the partition plate unit, in which the partition plate, the resin-molded piece and the spring means are unitized with one another, is retained movably in the direction of the optical axis of the optical fiber by the retaining portion. Therefore, even if variations occur in the length in the direction of the optical axis of the optical fiber of the optical plug, the partition plate unit is moved by the spring means so that the positional relation between the end surface of the optical plug and the partition plate becomes constant.
In one embodiment, the spring means of the partition plate unit are provided in at least two places located on a plane approximately perpendicular to the optical axis of the fiber and on a diagonal line of the resin molding.
With this arrangement, the partition plate unit can stably be moved by being urged in the direction of the optical axis of the optical fiber by a necessary minimum number of spring means without being inclined, and the reduction in size and the simplification of the partition plate unit can be achieved.
In one embodiment, the partition plate and resin-molded piece of the partition plate unit are formed into one piece by insert molding.
This arrangement enables an easy assembling of the module, in comparison with a case of combining small separate members, which leads to a difficult assembling. Also, the required dimensional accuracy can easily be obtained so that high-quality optical transmission by the full-duplex communication method can be achieved. In addition, the partition plate unit can be downsized.
In one embodiment, the partition plate of the partition plate unit has a planar opposed surface that faces an end surface of the optical fiber with a gap therebetween when the optical plug is placed in position within the module.
With this arrangement, dimensional accuracy of the planar opposed surface with respect to the optical fiber end surface can easily be obtained. Also, the partition plate having the planar surface can be processed at lower cost than when having a curved opposed surface.
In one embodiment, an optical absorption layer is provided on the opposite surface of the partition plate.
With this arrangement, the signal light emitted from the end surface of the optical fiber is prevented from being reflected by the opposed surface of the partition plate, to which the emitted signal light first gets.
In one embodiment, the engagement surface of the resin-molded piece comes in contact with a peripheral edge portion of the end surface of the optical plug. Therefore, the positional adjustment of the end surface of the optical plug can easily be achieved without damaging the optical fiber end surface.
In one embodiment, the partition plate is sized such that a distance in a direction of optical axis from said end surface of the optical fiber to an end opposite from the optical fiber of the partition plate is greater than distances in a direction of optical axis from said end surface of the optical fiber to each of a bottom of a transmission lens provided on emission side of the light-emitting element and a bottom of a reception lens provided on incident side of the light-receiving element.
With this arrangement, the transmission signal light (including reflection light) emitted from the light-emitting element is reliably prevented from being incident on the light-receiving element, so that the optical crosstalk can effectively be reduced.
By employing the above-mentioned optical transmitter-receiver module, there can be provided electronic equipment such as an information domestic appliance capable of performing optical transmission by a high-quality full-duplex communication system.